Scaffolds
Diseases | Insects | Credits
SCAFFOLDS Fruit Journal, Geneva, NY                Volume 4
Update on Pest Management and Crop Development      May 30, 1995

COMING EVENTS

                                                     43F       50F
Current DD accumulations (Geneva 1/1-5/30):          648       340
                       (Highland 3/1-5/29):          668       336

Coming Events:                              Ranges:
Spotted tentiform leafminer sap-feeders present  295-628    146-325
Plum curculio oviposition                        448-670    232-348
Spotted tentiform leafminer 1st flight subsides  489-978    270-575
Redbanded leafroller 1st flight subsides         518-893    255-562
American plum borer 1st flight peak              535-962    273-601
Codling moth 1st flight peak                    547-1326    307-824
Peachtree borer 1st catch                       565-1557    299-988
San Jose scale 1st flight peak                   581-761    308-449
Obliquebanded leafroller pupae present           612-860    330-509

PHENOLOGIES: 
Geneva, 5/30
   Apple (McIntosh): Fruit Set
   Pear: (Red Delicious): Petal Fall

TRAP CATCHES (Number/trap/day)
Geneva:   
                                  5/15   5/17   5/22   5/25   5/30
Green Fruitworm                    0.3      0      0      0      0
Redbanded Leafroller               2.0    1.3    1.3    1.0    0.2
Spotted Tentiform Leafminer        492    812    202    108     63
Oriental Fruit Moth (apple)       57.0   71.0   10.9    9.5    2.1
Lesser Appleworm                  28.9   14.0   12.2   15.0    6.9
Codling Moth                         -    6.0*   2.3    3.7    1.9
San Jose Scale                     0.1*     0    0.1    1.0      0
American Plum Borer (cherry)       0.1*   1.0    0.4    1.8    0.8
Lesser Peachtree Borer (peach)       -      -      0    0.3*   1.1
Lesser Peachtree Borer (cherry)      -      -      0      0    0.6*


Highland (Dick Straub, Peter Jentsch)
                                   5/8   5/15   5/22   5/29
Green Fruitworm                      0      0      0      0
Redbanded Leafroller               0.8    0.7    0.6   <0.1
Spotted Tentiform Leafminer        6.0    8.2    2.6    0.5
Oriental Fruit Moth                0.8    1.0      0    0.5
Fruittree Leafroller               0.1*   0.2      0      0
White Apple Leafhopper nymphs      0.1*  <0.1      -   <0.1
Codling Moth                         -   <0.1*   1.9    4.6
Lesser Appleworm                     -      -    1.0*  <0.1
Sparganothis Fruitworm               -      -      0      0
Tufted Apple Budmoth                 -      -   <0.1*   1.1
                                                       * = 1st catch

PEST FOCUS
Geneva: Lesser Peachtree Borer 1st catch, 5/25
Highland: 1st Plum Curculio oviposition scars in apples, 5/23; 1st Rose 
  Leafhopper on floribunda rose.

APPLE DISEASE UPDATE

By:Dave Rosenberger, Plant Pathology, Highland

APPLE SCAB

Although we received relatively little rain during the past two weeks, we have had extended periods of cool damp weather. These conditions are ideal for development of apple scab, especially secondary scab. The availability of scab ascospores drops off rapidly after petal fall, so orchards with no visible scab 10 days after petal fall will be at minimal risk for the remainder of the season. In these orchards, scab and summer diseases can probably be controlled with fungicides applied at 14-21 day intervals, depending on weather conditions. However, where apple scab became established in trees during prebloom infection periods, there is continued risk of severe scab. Secondary scab is now "blossoming" in our unsprayed trees with numerous lesions appearing on fruit and on early terminal leaves. This is a critical time to carefully evaluate orchards for incidence of apple scab. Where lesions are present on newly developing terminal leaves, eradicant sprays (SI fungicide plus captan) should be applied as soon as possible, and the orchard manager may wish to seek divine intervention (in the form of hot weather!) to help slow the spread of secondary scab.

SCARF SKIN

A fruit finish disorder known as scarf skin has become increasingly important as successful apple marketing has become more competitive and more dependent on physical appearance of the fruit. Scarf skin is a disorder that makes the waxy surface of fruit appear milky or cloudy. Researchers in the Cumberland-Shenandoah region have also referred to this disorder as "opalescence". The disorder is particularly severe on 'Stayman' and 'Law Rome', but it can appear on nearly all cultivars in severe years.

A description of the disorder and the origin of the term "scarf skin" dates back to the 1905 publication of "The Apples of New York" by Beach et al. They described scarf skin as "a dull or clouded appearance to the red skin as in 'Sweet Winesap' or 'Black Gilliflower'". Researchers have since shown that the disorder occurs when the epidermis and cuticle separate from the underlying tissue. The resulting air space beneath the waxy fruit surface disrupts light transmission and produces the milky or cloudy appearance. Unfortunately, we still do not understand what causes scarf skin to develop. Various researchers have noted that scarf skin is consistently more severe in some orchard blocks than in others. We also know that some cultivars are more susceptible than others and that the problem is more severe in some seasons than in others.

Scarf skin was studied by Dr. David Ferree and coworkers in Ohio in the early 1980's (see the two articles cited below). By bagging 'Rome Beauty' fruit clusters in polyethylene bags at various times beginning at petal fall, they were able to demonstrate that scarf skin is initiated between petal fall and 60 days after petal fall. Fruit bagged for 60 days had no scarf skin. The greatest amount of scarf skin was initiated close to petal fall, and the severity of scarf skin from later exposures decreased gradually. Fruit protected for 40 days showed very little scarf skin. Severity of scarf skin was not affected by applications of Solubor, calcium chloride, or dimethoate, but it was reduced by applications of giberellic acid (GA4+7).

Ferree and coworkers also showed that scarf skin was significantly more severe on trees receiving a seasonal program of Benlate or Dikar fungicides than on trees sprayed with Polyram, Dodine, Captan, or mancozeb. However, these fungicides do not consistently cause a scarf skin problem. Other researchers have compared various fungicides for their impact on scarf skin and have found that, in some seasons and some orchards, Benlate and Dikar had no deleterious effects. Nevertheless, the work by Ferree and observations that I have made in New York both support the hypothesis that Benlate applied within 40 days of petal fall can contribute to development of scarf skin in some years. (No other fungicide appears to stimulate scarf skin as frequently or as severely as does Benlate.) The effect of Benlate is probably dependent on interactions with environmental and possibly nutritional conditions at critical periods in the development of the fruit.

The period of greatest mechanical stress at the surface of rapidly growing apple fruits occurs as fruit reach approximately one inch in diameter, and this period coincides with the period of high susceptibility to both scarf skin and russet. Probably any factors that contribute to stressing the fruit during this critical period may promote scarf skin development. Various researchers have shown that environmental conditions during the 40 days after bloom are important in determining the amount of scarf skin that will develop, but the exact weather conditions that contribute to scarf skin have not been defined. Ferree et al. suggest that climatic changes that stress fruit during the critical period after petal fall may contribute to scarf skin. Thus, a period of cool, rainy weather followed by a hot, sunny, windy day might constitute a stress that could cause the separation in cell layers that results in scarf skin. An application of Benlate during this critical time might decrease elasticity of the cells on the fruit surface and thereby contribute further to the problem, whereas Benlate applications under other conditions may have no adverse effects. Given the current state of our knowledge (or lack thereof), we cannot provide recommendations that ensure scarf skin will not appear. We can only suggest that growers concerned about this problem avoid using Benlate during the 40 days after petal fall and, if possible, irrigate trees as needed to minimize water stress during this same critical period of fruit development.

Published information on scarf skin:

  • Ferree, D. C., Darnell, R. L., Fox, R. D., Grazee, R. D., and Wittmoyer, R. E. 1984. Environmental and nutritional factors associated with scarf skin of 'Rome Beauty' apples. J. Amer. Soc. Hort. Sci. 109:507- 513.
  • Ferree, D. C., Ellis, M. A., and Bishop, B. L. 1984. Scarf skin on 'Rome Beauty': Time of origin and influence of fungicides and GA4+7. J. Amer. Soc. Hort. Sci. 109:422-427.


    INSECT BITES

    By:Art Agnello, Entomology, Geneva

    OBLIQUEBANDED LEAFROLLER

    Various field reports attest to the existence of healthy levels of OBLR in the usual problem areas this season, now evident as fruit cluster infestations by overwintered generation larvae. Although the economics of controlling this brood don't always work out in terms of early-season damage prevented, many growers like to hedge their bets against the summer brood numbers by including something in the petal fall spray to take care of as many susceptible larvae as possible. For problem blocks, we would recommend Dipel, Lannate or Lorsban, together with an admonition to be extremely timely with summer brood sprays when they become necessary.

    Apropos of which, Harvey Reissig's chemical control trials against OBLR in two Orleans Co. orchards last year generated some noteworthy results. He tested two basic spray timings using Lorsban: 2 applications, starting on July 7 (640 DD base 50F after the first adult catch) and July 22; and 3 applications, starting June 20, estimated to coincide with first hatch of the summer larvae, plus July 7 and July 22. The 3-spray program was also conducted using Asana and Guthion. The conclusive results showed the best control was obtained with the Asana program. The 2- and 3-spray programs of Lorsban were equally effective. Lorsban was more effective than Guthion in only one orchard, the one with moderate OBLR pressure (4.3% fruit damage in the check; the other had 36.3% fruit damage). These results indicate that the OBLR in these two orchards are almost as resistant to Lorsban as they are to Guthion, which has been considered ineffective for many years.

    What does this mean to the average grower? First of all, these orchards should not necessarily be considered as representative of all commercial blocks in the state. We traditionally go to the worst trouble spots for these trials, and there are undoubtedly many orchards where Lorsban will still provide acceptable control of this pest. (Even Penncap-M still works pretty well in some spots, so you should be the expert regarding the activity of various products on your own farm.) However, the message from these trials is that this insect's inevitable march towards resistance to the commonly used materials is indeed proceeding, as we have feared. It so happens that the once-pronounced resistance OBLR showed to pyrethroids appears to have subsided somewhat for the time being, and it may be possible to squeeze a couple of years' worth of control out of an Asana program before it resurfaces. Naturally, we make this statement with the appropriate cautions about its potentially detrimental effects on mite control programs, but in this case there simply is no easy way out.

    The good news is that in all likelihood, by the time Asana's effectiveness begins to flag once again, we will probably have registrations for some of the new insect growth regulator compounds currently rounding the regulatory bend for OBLR control. These include Comply (fenoxycarb) and Confirm (tebufenozide), both of which promise quite good activity on our favorite enemy. In the meantime, in sites where Lorsban has been showing signs of diminished capacity, use it only at petal fall in order to decrease selection pressure on the summer generation, against which you should elect either Asana or a short-interval (weekly) 4-5-spray low-rate B.t. program.

    SAN JOSE SCALE

    The San Jose scale (SJS) is a pest of tree fruit that attacks not only apple, but also pear, peach, plum, and sweet cherry. The minute SJS adult males emerge in the spring from beneath scale covers on the trees, usually during bloom, and mate. The first of this year's adults were recorded on 5/15 in our traps at Geneva. The females produce live crawlers within 4-6 weeks of mating; these are bright yellow, very tiny insects resembling larval spider mites. About 24 hours after birth, the crawlers have walked or drifted to new sites and settled in by inserting their mouthparts into the tree and secreting a white waxy covering that eventually darkens to black.

    SJS infestations on the bark contribute to an overall decline in tree vigor, growth, and productivity. Fruit feeding causes distinct red-purple spots that decrease the cosmetic appeal of the fruit. Control measures for SJS are recommended when the scale or their feeding blemishes have been found on fruit at harvest during the previous season. Insecticidal sprays are most effective when directed against the first generation crawlers, specifically timed for the first and peak crawler activity, which are usually 7-10 days apart. The most reliable method of determining first appearance of the crawlers in your specific area is by putting sticky-tape traps on the tree limb near encrusted areas and checking them at least twice a week, starting next week. Alternatively, a degree-day accumulation of 310 (50 F base) from the date of first adult catch has also been shown to be reliable if the degree-days are known with some accuracy.

    Effective materials for SJS control include Lorsban 50WP, Guthion, Imidan and Penncap-M. These sprays may also help in the control of OBLR, apple maggot, and codling moth. Coverage and control are generally better if the pesticide is applied dilute and in every row. SJS is frequently a problem in larger, poorly pruned standard size trees that do not receive adequate spray coverage. Dormant or delayed-dormant sprays of oil, or 1/2-inch green applications of Lorsban 4EC or Supracide will help prevent populations from getting established. Early season pruning is important for removing infested branches and suckers, as well as for opening up the canopy to allow better coverage in the tree tops where SJS are often concentrated.

    PEAR PSYLLA

    Psylla numbers are on the rise in many pear orchards, easily approaching the 1-2 nymph/leaf threshold we consider appropriate for an Agri-Mek or Mitac application. This should be the week designated as the suitable time to begin those sprays in the Hudson Valley, with most western New York orchards coming due by week's end and next week. Tree condition appears to be good, so foliage should be succulent enough to absorb the material. We would reiterate our recommendation to use the high rate of 20 fl. oz. of Agri-Mek mixed with 1 gallon of Ultra Fine oil per acre, in order to maximize the treatment's effectiveness.

    CHERRY FRUIT FLIES

    No adults have been reported caught on sticky boards yet, but because of the zero tolerance in cherries for insect damage or presence, this absence does not diminish the need for sprays in your cherries now (for these pests as well as for curculio). Guthion, Imidan (tart cherries only), Sevin, the pyrethroids, or Penncap-M are all effective treatments. Sevin, Imidan and Penncap-M will also control black cherry aphid.

    RE-ENTRY INTERVALS AND THE RECOMMENDS

    ByArt Agnello, Entomology, Geneva The Tree-Fruit Recommendations have traditionally included some sort of listing of the commonly used pesticides along with a designation regarding the required period of time one must wait to enter a treated area without protective equipment. This re-entry interval, or REI, commonly fell into the category of 24, 48 or 96 hrs, plain and simple, so we could just stick "@" signs in front of the pesticide name, as in Table 40 (p. 172) of this year's Recommends. However, since the advent of the Worker Protection Standard, this matter has gotten considerably more complicated, and involves the particular use of the product, the specific activity being conducted in a treated area, and sometimes differing levels of protective equipment needed. For this reason, I've decided to take a pass on providing all this complex information in the Recommends for the time being, until such time as the WPS process sorts itself out a little more and we can decide whether we should even attempt to stuff the Recommends with more information that arguably might be better obtained by just reading the label, which everyone should be doing anyway. For the moment, don't assume that the "@" designations are completely accurate in Table 40 of the 1995 Tree-Fruit Recommendations, because they're not.

    WHAT DO YOU EXPECT?

    By:Dave Kain and Art Agnello, Entomology, Geneva

    Some of the most frequent comments and questions put to us over the course of the season during a given year, particularly during the first part of the season, have to do with "how we're doing" on pest and tree development in comparison with last year, or with a "normal" year. Naturally, although some of this is only idle curiosity, sometimes a few good clues about the season can be gathered by comparing the relative timings of yearly events -- are the trees ahead of the insects, are some pests out of sync with the season while others aren't, is everything behind schedule? We don't pretend to possess any startling insight about how things are going this year, but we thought it might be worthwhile to provide some comparative listings of a few noteworthy events this year, as well as for 1994 and for the calculated "normal" occurrence, based on however many observations we have on record. The following Progression Of Events gives degree-day values for some arbitrarily selected happenings:

                                                Normal   1994   1995
    DD (base 43F) accumulation to date (5/30):     691    557    648
    Pear Psylla 1st oviposition                     80     49    111
    Pear Psylla 1st nymphs present                 242    257    236
    Green Fruitworm peak flight                    134    118    230
    European Red Mite hatch begins                 284    257    290
    Redbanded Leafroller 1st flight peak           298     ND    406
    Spotted Tentiform Leafminer 1st flight peak    308    372    439
    Oriental Fruit Moth 1st flight peak            428    372    439
    Codling Moth 1st catch                         484    450    439
    Lesser Peachtree Borer 1st catch               589    581    563
    McIntosh at full bloom                         377    372    406
    McIntosh at petal fall                         484    450    563
    

    Scaffolds is published weekly from March to September by Cornell University -- NYS Agricultural Experiment Station (Geneva), and Ithaca -- with the assistance of Cornell Cooperative Extension. New York field reports welcomed. Send submissions by 3 p.m. Monday to:

    Scaffolds Fruit Journal
    Editors: A. Agnello, D. Kain
    Dept. of Entomology, NYSAES
    Geneva, NY 14456-0462
    Phone: 315-787-2341 FAX:315-787-2326
    E-mail: art_agnello@cornell.edu

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